Virtual visitor location register for a wireless local area network

ABSTRACT

A multi-mode mobile station is able to wirelessly communicate with a wireless wide area network (WWAN) and with a wireless local area network (WLAN). The WLAN includes a “virtual” visitor location register (VVLR) for storing information about multi-mode mobile stations being served by the WLAN. The VVLR communicates with a home location register (HLR) in the WWAN in order to facilitate roaming between the WWAN and WLAN by the multi-mode mobile station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/161,497, filed Jun. 3, 2002, which is incorporated herein byreference.

BACKGROUND

1. Field of the Invention

The present invention relates to telecommunications and, moreparticularly, to a “virtual” visitor location register for a wirelesslocal area network.

2. Description of Related Art

A traditional enterprise telephone network includes a number of landlineextension telephones (either analog or digital) connected to a privatebranch exchange (PBX). The PBX, in turn, is connected to the publicswitched telephone network (PSTN), e.g., via a primary rate interface ora basic rate interface. Increasingly, however, more diverse types ofcommunication devices are being used in enterprise networks. Forexample, the PBX may be connected via a local area network (LAN) topacket-based communication devices, such as voice-over-packet (VoP)telephones or audio-equipped personal computers. In addition, the PBXmay be an “IP-PBX” communicatively coupled to a packet-switched network,such as the Internet, instead of or in addition to the PSTN.

The PBX may also be part of a wireless local area network (WLAN) thatincludes one or more wireless access points for communicating withmobile stations over air interfaces. Such mobile stations may includewireless telephones, wirelessly-equipped personal digital assistants(PDAs), wirelessly-equipped laptop computers, and/or other wirelesscommunication devices. The air interface communications may conform to aWLAN specification, such as IEEE 802.11b, Bluetooth, HomeRF, orHiperLAN. Alternatively, or additionally, the air interfacecommunication may occur in a cordless telephone format, in aMultichannel Multipoint Distribution Service (MMDS) format, or in someother format. Some of these mobile stations may also be able tocommunicate with a wireless wide area network (WWAN), using an airinterface format such as CDMA or GSM. Thus, when a multi-mode mobilestation is within the wireless coverage area of the WLAN, it may use theWLAN for communication, and when the multi-mode mobile station is withinthe wireless coverage of the WWAN, it may use the WWAN forcommunication.

WWAN signaling protocols, such as IS-41, typically support roamingbetween areas served by different serving systems. For example, eachserving system in a WWAN may include a visitor location register (VLR)that communicates with a home location register (HLR) for mobilitymanagement and other purposes. Now, with the interest in multi-modemobile stations that may be in communication with either a WWAN or aWLAN at any given time, there is a need to provide additional systemsand methods for mobility management in order to facilitate roamingbetween the WWAN and WLAN. For example, it is desirable to be able toreach a multi-mode mobile station by dialing the same directory number,regardless of whether the multi-mode mobile station is in communicationwith the WWAN or with the WLAN.

SUMMARY

In a first principal aspect, an exemplary embodiment of the presentinvention provides a wireless local area network (WLAN) for providingwireless telecommunications services to a multi-mode mobile station. Themulti-mode mobile station is able to wirelessly communicate with awireless wide area network (WWAN) when operating in a first wirelesscoverage area. The WWAN includes a first data register that contains afirst data record for the multi-mode mobile station. The WLAN comprisesat least one wireless access point, a private branch exchange (PBX)communicatively coupled to the at least one wireless access point, and asecond data register communicatively coupled to the PBX and to the firstdata register. The at least one wireless access point provides a secondwireless coverage area, within which the multi-mode mobile station isable to wirelessly communicate with the at least one wireless accesspoint. The second data register is able to transmit at least onemobility management message to the first data register. The at least onemobility management message facilitates roaming between the first andsecond wireless coverage areas by the multi-mode mobile station.

In a second principal aspect, an exemplary embodiment of the presentinvention provides a method of mobility management of a multi-modemobile station that is able to wirelessly communicate with a wirelesswide area network (WWAN) and with a wireless local area network (WLAN).In accordance with the method, the multi-mode mobile station associateswith a wireless access point of the WLAN. The WLAN includes a privatebranch exchange (PBX). The PBX stores information regarding themulti-mode mobile station in a WLAN data register. The WLAN dataregister sends a registration message to a WWAN data register in a WWAN.The registration message identifies the multi-mode mobile station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of a wireless telecommunicationssystem, in accordance with an exemplary embodiment of the presentinvention;

FIG. 2 is a simplified call flow diagram illustrating a registrationprocess, in accordance with an exemplary embodiment of the presentinvention;

FIG. 3 is a simplified call flow diagram illustrating signaling to setup a call, in accordance with an exemplary embodiment of the presentinvention; and

FIG. 4 is a simplified call flow diagram illustrating signaling to setup a call, in accordance with an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention, in exemplary embodiments, facilitates the roamingof multi-mode mobile stations between a wireless wide area network(WWAN) and a wireless local area network (WLAN). In an exemplaryembodiment, a multi-mode mobile station may be reached by dialing thesame directory number, regardless of whether the multi-mode mobilestation is in communication with the WWAN or with the WLAN. A PBX of theWLAN is provided with a data register that keeps track of whichmulti-mode mobile stations are registered for services with the PBX. Forconvenience, this data register is referred to herein as a “virtual”visitor location register (VVLR), though it is to be understood that aVVLR need not perform all of the same functions or engage in the samesignaling as a VLR would in a WWAN.

As used herein, a “WLAN” refers to a local area network that includes atleast one wireless access point. Thus, in a WLAN, some devices maycommunicate wirelessly, but other devices may communicate over wiredcommunications. As used herein, a “PBX” refers to a system that controlstelephony services in the WLAN. Preferably, the PBX is an “IP-PBX”communicatively coupled to a packet-switched network. Alternatively oradditionally, the PBX may be connected to the PSTN, e.g., via a primaryrate interface or a basic rate interface. The PBX may be directlyconnected to the WLAN. Alternatively, the PBX could be communicativelycoupled to the WLAN so as to control telephony services in the WLANremotely. In addition, the PBX could be provided as a single device oras a distributed system. Thus, the PBX could be a hosted PBX or anIP-Centrex system, for example. The VVLR may be integrated with orotherwise accessible by the PBX.

The VVLR for the WLAN communicates with a home location register (HLR)for the WWAN in order to help manage the mobility of multi-mode mobilestations. In an exemplary embodiment, the communications between theVVLR and the HLR may conform to a WWAN signaling protocol, such asIS-41. However, other signaling protocols, such as SIP, SIP-T, or H.323could be used. In addition, the VVLR may communicate using one protocol,such as SIP, and the HLR may communicate in another protocol, such asIS-41, with a signaling gateway converting between the two protocols.Such conversion may involve encapsulation/de-encapsulation, e.g., ofIS-41 messages in SIP or SIP-T messages. Alternatively or additionally,the conversion may involve translation, i.e., mapping between messagetypes and/or parameters.

In the example where the VVLR and HLR both communicate using IS-41, theVVLR may send an IS-41 Registration Notification (REGNOT) message to theHLR when a multi-mode mobile station registers for services in the WLAN.In this way, the HLR is notified that the multi-mode mobile station isan area being served by the VVLR. Then, when a call is placed to adirectory number associated with the multi-mode mobile station, the HLRmay send an IS-41 Routing Request (ROUTEREQ) message to the VVLR toobtain routing information that can be used to route the call to themulti-mode mobile station. The routing information could be a directorynumber assigned to the PBX, in which case the call may be routed to thePBX via the PSTN. Alternatively, the routing information could result inthe call being routed to the PBX via a packet-switched network. Inparticular, the routing information could be a directory number assignedto a media gateway communicatively coupled to the PBX via apacket-switched network, or the routing information could be an InternetProtocol (IP) address of the PBX or of the multi-mode mobile station.Other types of routing information could also be used.

In addition to REGNOT and ROUTEREQ messages, the VVLR and HLR couldexchange other messages, for mobility management purposes or for otherpurposes. The VVLR may also store a data record for each multi-modemobile station being served by the WLAN. The data record may include aservice profile that the VVLR obtained from the HLR, e.g., in responseto a REGNOT message. In this way, the services available to themulti-mode mobile station when served by the WWAN may also be availableto the multi-mode mobile station when served by the WLAN.

1. EXEMPLARY NETWORK ARCHITECTURE

FIG. 1 is a simplified block diagram of an exemplary wirelesstelecommunications system 10. In FIG. 1, connections that carry voice orother media are shown as solid lines and connections that carryprimarily signaling are shown as dashed lines.

Wireless telecommunications system 10 includes network elements thatfunction together as a wireless wide area network (WWAN) 12 and networkelements that function together as a wireless local area network (WLAN)14. WWAN 12 may provide wireless coverage in a relatively largegeographic area, such as an entire city, often by using a plurality ofcontiguous wireless coverage areas, such as cells or sectors. Thewireless communication in WWAN 12 may occur in an analog format, such asthe Advanced Mobile Phone Service (AMPS), or in a digital format, suchas code division multiple access (CDMA), time division multiple access(TDMA), or Global System for Mobile communication (GSM). The wirelesscommunication may occur in licensed frequency bands, such as the 1.9 GHzPCS bands. WLAN 14 may provide wireless coverage in a relatively limitedarea, as compared to WWAN 12, such as in a building or part of abuilding. In addition, WLAN may use one or more unlicensed frequencybands, such as the unlicensed frequency band in the 2.4 GHz range.

A multi-mode mobile station 16 is able to wirelessly communicate withWWAN 12 and with WLAN 14. More particularly, multi-mode mobile station16 is able to communicate with WWAN 12 when operating in an area servedby WWAN 12 and is able to communicate with WLAN 14 when operating in anarea served by WLAN 14. In some areas, the wireless coverage of WWAN 12and WLAN 14 may be overlapping, and multi-mode mobile station 16 maydecide whether to communicate with WWAN 12, with WWAN 14, or with both.Multi-mode mobile station 16 may be a wireless telephone,wirelessly-equipped personal digital assistants (PDA),wirelessly-equipped laptop computer, or other type of wirelesscommunication device.

WWAN 12 may include a base transceiver station (BTS) 18 that provides awireless coverage area within which BTS 18 may communicate with one ormore mobile stations, such as multi-mode mobile station 16, over an airinterface 20. Although FIG. 1 shows only BTS 18, WWAN 12 may include aplurality of BTSs that may provide a plurality of wireless coverageareas. The communications between BTS 18 and multi-mode mobile station16 may occur in a digital format, such as CDMA, TDMA, GSM, or they mayoccur in an analog format, such as AMPS. A preferred wirelesscommunications format is cdma2000 such as described in EIA/TIA/IS-2000Series, Rev. A (published March 2000), which is incorporated herein byreference.

BTS 18 may be controlled by a base station controller (BSC) 22, which,in turn, may be controlled by a mobile switching center (MSC) 24.Although FIG. 1 shows only one MSC and only one BSC, WWAN 12 may includea plurality of MSCs, which may, in turn, control a plurality of BTSs,via a plurality of BSCs. MSC 24 also has access to a visitor locationregister (VLR) 26. VLR 26 stores data records for mobile stations, suchas multi-mode mobile station 16, that are being served by MSC 24. A datarecord stored in VLR 26 for a mobile station typically identifies themobile station, e.g., by mobile identification number (MIN), mobiledirectory number (MDN), mobile station identification (MSID), and/orelectronic serial number (ESN). The data record may also include statusinformation for the mobile station, such as whether the mobile stationis busy, and may also include a service profile that identifies theservices to which the mobile station subscribes. The data record mayalso include other information relating to the mobile station. VLR 26may obtain some of the information in the data record for the mobilestation from a home location register (HLR) 28 associated with themobile station, e.g., using IS-41 signaling. Although FIG. 1 shows VLR26 as a network element separate from MSC 24, VLR 26 may be integratedor co-located with MSC 24.

In the example shown in FIG. 1, WWAN 12 is the “home” network ofmulti-mode mobile station 16, in that WWAN 12 includes a home locationregister (HLR) 28 associated with multi-mode mobile station 16. HLR 28stores a data record for multi-mode mobile station 16. The data recordstored in HLR 28 for multi-mode mobile station 16 identifies multi-modemobile station 16, such as by MDN, MIN, MSID, and/or ESN and includes alast known location of multi-mode mobile station 16, e.g., identifiesthe VLR that most recently registered multi-mode mobile station 16 withHLR 28. The data record may also include status information formulti-mode mobile station 16, a service profile for multi-mode mobilestation 16, and other information relating to multi-mode mobile station16. WWAN 12 may also include a service control point (SCP) 29. SCP 29may include service logic that specifies how to providetelecommunications services to mobile stations such as multi-mode mobilestation 16.

MSC 24 is connected to the public switched telephone network (PSTN) 30.PSTN 30 may use an out-of-band signaling system, such as SignalingSystem 7 (SS7) to route calls. Thus, PSTN 30 may include acircuit-switched network 32 that carries bearer traffic, i.e., the voiceor other media in calls, and a signaling network 34 that carriessignaling traffic used to set up, tear down, monitor, and control calls.Circuit-switched network 32 may include a plurality of trunks, with eachtrunk carrying media in a pulse code modulation (PCM) format in aplurality of time-domain multiplexed channels. Signaling system 34 mayinclude a plurality of networked signal transfer points (STPs).

MSC 24 may communicate with signaling network 34, e.g., using SS7, toroute calls via circuit-switched network 32 to and from mobile stationsbeing served by WWAN 12, such as multi-mode mobile station 16. Toprovide telecommunications services to mobile stations being served byWWAN 12, such as multi-mode mobile station 16, MSC 24 may alsocommunicate with HLR 28 and SCP 29 via signaling network 34. Thecommunications between MSC 24 and HLR 28 may conform to IS-41specifications. A recent revision of the IS-41 specifications,ANSI/TIA/EIA-41-D-97, published in December 1997, is incorporated hereinby reference. The communications between MSC 24 and SCP 29 may conformto the specification “Wireless Intelligent Network,” TIA/EIA/IS-771,published in July 1999, which is incorporated herein by reference. TheIS-41 and IS-771 signaling may be carried in an SS7 application layer insignaling network 34.

Using SS7, IS-41, IS-771, and/or other signaling carried in signalingnetwork 34, MSC 24 may connect incoming calls from PSTN 30 to multi-modemobile station 16, which calls may originate from calling parties usinglandline telephones, mobile stations, or other communication devices.Similarly, MSC 24 may use SS7, IS-41, IS-771, and/or other signalingcarried in signaling network 34 to route calls originating frommulti-mode mobile station 16 through PSTN 30. In addition, MSC 24 may bea “home” MSC of multi-mode mobile station 16, in that multi-mode mobilestation 16 may have a mobile directory number (MDN) that is assigned toMSC 24. Thus, calls placed to this MDN may be routed to MSC 24 by PSTN30.

WLAN 14 includes a private branch exchange (PBX) 36 that may becommunicatively coupled to a variety of wireline and/or wirelesscommunication devices. For example, PBX 36 may be connected to analogtelephony devices, such as analog telephone 38, facsimile machines,and/or modems. PBX 36 may also be connected to digital telephonydevices, such as digital telephone 40. PBX 36 may also becommunicatively coupled, e.g., via a local area network (LAN) 42, tocommunication devices that exchange media in a packet-based format. Forexample, LAN 42 may be connected to a voice-over-packet (VoP) telephone44 and to a personal computer 46, equipped for audio communication,e.g., equipped with a microphone and speaker. LAN 42 may also connectedto one or more wireless access points, such as wireless access point 48.LAN 42 may also be connected to other devices.

Wireless access point 48 provides a wireless coverage area within whichwireless access point 48 is able to communicate with wirelesscommunication devices, such as multi-mode mobile station 16, over an airinterface 50. More particularly, wireless access point 48 maycommunicate with multi-mode wireless communications devices, e.g., thatare able to communicate with both a WWAN, such as WWAN 12, and a WLAN,such as WLAN 14. Wireless access point 48 may also communicate withwireless communication devices that may only be able to communicate withWLANs such as WLAN 14. The wireless communication between wirelessaccess point 48 and multi-mode mobile station 16 may conform to or makeuse of IEEE 802.11a, IEEE 802.11b, IEEE 802.11e, IEEE 802.11g, or IEEE802.11h standards (referred to generally herein as “802.11x”), orvariations thereof. These 802.11x standards are incorporated herein byreference. Alternatively or additionally, the wireless communication mayconform to or make use of Bluetooth specifications, HomeRFspecifications, of HiperLAN standards, or may occur in a cordlesscommunication format or a Multichannel Multipoint Distribution Service(MMDS) format, or may involve some other protocol or format.

PBX 36 may be connected to PSTN 30, e.g., to both circuit-switchednetwork 32 and signaling network 34. Thus, PBX 36 may be able toterminate calls to and originate calls from communication devicescoupled to PBX 36, via PSTN 30. Alternatively, or additionally, PBX 36may be an “IP-PBX” connected to a packet-switched network 52, e.g., viaLAN 42 and a router 54. Thus, PBX 36 may be able to terminate calls toand originate calls from communication devices coupled to PBX 36, viapacket-switched network 52. If PBX 36 is connected to both PSTN 30 andpacket-switched network 52, then PBX 36 may use PSTN 30 for some callsand may use packet-switched network 52 for other calls. For example, PBX36 may preferentially use PSTN 30 to originate calls from certaincommunication devices, e.g., analog telephone 38 and digital telephone40, but PBX 36 may preferentially use packet-switched network 52 tooriginate calls from certain other communication devices, e.g., VoPtelephone 44, audio-equipped computer 46, and wireless devices incommunication with wireless access point 48, such as multi-mode mobilestation 16. As another example, PBX 36 may preferentially usepacket-switched network 52 for certain types of calls, such aslong-distance calls.

Packet-switched network 52 may include one or more local area networks(LANs) and/or one or more wide area network (WANs), such as theInternet. Packet-switched network 52 may route packets using a networkprotocol, such as the Internet Protocol (IP), in combination with theUser Datagram Protocol (UDP) or Transmission Control Protocol (TCP). TheIP packets may be carried over lower level protocols, such asasynchronous transfer mode (ATM) protocols. Protocols, such as theReal-Time Transport Protocol (RTP), may be used to carry voice or othermedia through packet-switched network 52 in a real-time format. Relevantaspects of RTP are described in Schulzrinne, et al., “RTP: A TransportProtocol for Real-Time Applications,” Request for Comments 1889 (January1996), which is incorporated herein by reference.

Other protocols, such as the Session Initiation Protocol (SIP) or theSession Initiation Protocol for Telephones (SIP-T), may be used to setup and/or manage communication sessions through packet-switched network52. Relevant aspects of SIP are described in Rosenberg, et al., “SIP:Session Initiation Protocol,” Request for Comments 3261 (June 2002),which is incorporated herein by reference. Relevant aspects of SIP-T aredescribed in Vemuri, et al., “Session Initiation Protocol for Telephones(SIP-T): Context and Architectures,” Request for Comments 3372(September 2002), which is incorporated herein by reference. SIP and/orother protocols may, in turn, use the Session Description Protocol (SDP)to describe the communication sessions that are being set up or managed.Relevant aspects of SDP are described in M. Handley, et al., “SDP:Session Description Protocol,” Request for Comments 2327 (April 1998),which is incorporated herein by reference.

In an exemplary embodiment, SIP is used to set up calls throughpacket-switched network 52 that involve WLAN 14. WLAN 14 may include oneor more SIP user agents for this SIP signaling. For example, PBX 36 mayinclude a SIP user agent to engage in SIP signaling on behalf ofcommunication devices coupled to PBX 36. Alternatively or additionally,one or more communication devices coupled to PBX 36 may have SIP useragents of their own. For example, multi-mode mobile station 16 may haveits own SIP user agent.

WLAN 14 also includes a virtual visitor location register (VVLR) 56 thathelps to manage the mobility of multi-mode mobile stations, such asmulti-mode mobile station 16. VVLR 56 may be integrated or co-locatedwith PBX 36, as shown in FIG. 1. Alternatively, VVLR 56 may be providedin a separate network element that is accessible by PBX 36, e.g., viaLAN 42. As described in more detail below, VVLR 56 communicates with HLR28 for mobility management purposes. More particularly, VVLR 56 maycommunicate with HLR 28 using IS-41 or some other protocol, such as SIP,SIP-T, or H.323, and one or more other network elements may convertbetween the protocols used by VVLR 56 and the protocols used by HLR 28.VVLR 56 may also store data records for the multi-mode mobile stationsbeing served by WLAN 14. For example, a data record stored in VVLR 56for multi-mode mobile station 16 may include one or more of thefollowing: the MAC and/or IP address of multi-mode mobile station 16,the user name and/or SIP address of the user of multi-mode mobilestation 16, and the MIN, MDN, MSID, and/or ESN of multi-mode mobilestation 16. Thus, VVLR 56 may play a role that is analogous to that ofan IS-41 VLR. However, VVLR 56 does not necessarily perform all of thefunctions of an IS-41 VLR and does not necessarily operate in accordancewith IS-41 specifications.

A call management service 58 may control calls and other communicationsessions in packet-switched network 52 that involve WLAN 14. Forexample, if SIP is used to establish, tear down, or otherwise managecalls through packet-switched network 52, call management service 58 mayfunction as a SIP proxy server and SIP registrar for WLAN 14. Thus, SIPuser agents in WLAN 14 may engage in SIP signaling with call managementservice 58 to register communication devices communicatively coupled toWLAN 14 and to originate and terminate calls through packet-switchednetwork 52 for such registered communication devices. Call managementservice 58 may also perform other functions. Although FIG. 1 shows callmanagement service 58 as a separate network element, call managementservice 58 may be integrated with another network element, such as amedia gateway controller.

Packet-switched network 52 may be communicatively coupled tocircuit-switched network 32 via a media gateway 60. Media gateway 60 mayconvert between media formats used in circuit-switched network 30 andpacket-switched network 52. For example, media gateway 60 may receivemedia from circuit-switched network 32 in a PCM format and convert themedia into an RTP format for transmission over packet-switched network52, and vice-versa.

A media gateway controller 62 may control media gateway 60, e.g., usingthe Media Gateway Control Protocol (MGCP). Relevant aspects of MGCP aredescribed in F. Andreason, et al., “Media Gateway Control Protocol(MGCP) Version 1.0,” Request for Comments 3435 (January 2003), which isincorporated herein by reference. Media gateway controller 62 may beconnected to signaling network 34 and to packet-switched network 52.Media gateway controller 62 may engage in SS7 or other signaling toroute calls to and from media gateway 60 through PSTN 30, and mediagateway controller may use SIP and/or other protocols to route calls toand from media gateway 60 through packet-switched network 52.

Thus, media gateway controller 62 may function as a signaling gateway,converting between legacy signaling protocols, such as SS7, IS-41,and/or IS-771, and voice-over-packet signaling protocols, such as SIP,SIP-T, and/or H.323. For example, PBX 36 and/or VVLR 56 may communicatewith HLR 28 and/or SCP 29 via media gateway controller 62, with mediagateway controller 62 converting between the SIP, SIP-T, H.323, or otherprotocols used by PBX 36 and/or VVLR 56 and the SS7, IS-41, IS-771, orother protocols used by HLR 28 and/or SCP 29. The conversions performedby media gateway controller 62 may involveencapsulation/de-encapsulation of messages and/or translation ofmessages, i.e., mapping between message types and message parameters.Media gateway controller 62 may also perform other functions. Forexample, call management service 58 may be a part of media gatewaycontroller 62.

Calls may reach media gateway 60 via PSTN 30 by routing to a directorynumber assigned to media gateway 60. If the directory number is alsoassociated with a network element accessible via packet-switched network52, such as a communication device in WLAN 14, then the call may also berouted from media gateway 60 through packet-switched network 52.However, calls may also reach media gateway 60 in other ways. Forexample, media gateway 60 may be integrated with other network elements,such as MSC 24. As a result, if a call is routed through PSTN 30 to MSC24, e.g., based on a directory number assigned to MSC 24, then MSC 24may not need to send the call again through PSTN 30 in order to have thecall reach packet-switched network 52. Instead, MSC 24 may use mediagateway 60 integrated with it to send the call directly topacket-switched network 52. As another example, media gateway 60 may beconnected to MSC 24 via an intermachine trunk (IMT) 64. In that case,MSC 24 may use a trunk and port number of IMT 64, instead of a directorynumber, to send a call to media gateway 60.

2. EXEMPLARY OPERATION

FIG. 2 illustrates an exemplary call flow that may be used to registermulti-mode mobile station 16. The process may begin when multi-modemobile station 16 transmits an association request, e.g., in accordancewith 802.11x protocols, to associate with wireless access point 48, asindicated by step 100. Step 100 may occur, for example, when multi-modemobile station 16 is being served by another wireless network, such asWWAN 12, or is not being served by any wireless network, but detectsradio frequency (RF) emissions from WLAN 14. Multi-mode mobile station16 may use a number of different methods to determine when to try todetect RF that may emanate from a WLAN. For example, multi-mode mobilestation 16 may periodically check for RF emissions in frequency bandsthat may be used by WLANs, e.g., frequency bands in the 2.4 GHz range.Alternatively, multi-mode mobile station 16 may use information aboutits current location to determine when to check for RF from WLANs.Examples of such approaches are described in a U.S. patent applicationSer. No. 10/391,158, titled “Method for Determining Availability of aRadio Network,” filed on Mar. 18, 2003, which is incorporated herein byreference. Step 100 may also occur when multi-mode mobile station 16 isbeing served by another wireless access point in WLAN 14 and moves intoan area in which wireless access point 48 provides better coverage.

It is to be understood that FIG. 2 shows step 100 in a simplified form.In particular, the signaling involved in associating with WLAN 14 maydepend on the particular air interface protocol that is used and mayinvolve the exchange of several messages between multi-mode mobilestation 16 and wireless access point 48. For example, the signaling mayinvolve procedures to authenticate multi-mode mobile station 16 foraccess to WLAN 14. For example, WLAN 14 may require multi-mode mobilestation 16 to transmit a valid username, password, PIN number, digitalcertificate, MAC address, or other code or identifier before grantingaccess. If the association request of step 100 is accepted, thenwireless access point 48 may transmit an association response indicatingthat multi-mode mobile station 16 is now associated with wireless accesspoint 48, as indicated by step 102. Multi-mobile station 16 may thentransmit a service registration message in order to register forservices with PBX 36, as indicated by step 104. The service registrationmessage may identify multi-mode mobile station 16, such as by IP addressand/or MAC address. The service registration message may conform to aprotocol such as H.323 or Cisco's Skinny Client Control Protocol. Otherprotocols could be used, however. A recent version of the H.323 protocolis described in International Telecommunication Union, RecommendationH.323, “Packet-based Multimedia System” (November 2000), which isincorporated herein by reference.

As indicated by step 106, PBX 36 may then send VVLR 56 a registrationnotification message to notify VVLR 56 that multi-mode mobile station 16has registered for services. The registration notification message mayalso identify multi-mode mobile station 16, such as by IP address and/orMAC address. In response to the registration notification of step 106,VVLR 56 may create or update a data record for multi-mode mobile station16. The data record may identify multi-mode mobile station 16, such asby IP address or MAC address. The data record may also include otherinformation relating to multi-mode mobile station 16. In some cases,VVLR 56 may update an existing data record for multi-mode mobile station16 when VVLR 56 receives the association notification of step 104. Inother cases, VVLR 56 may create a new data record for multi-mode mobilestation 16 in response to the association notification of step 106.

As noted above, VVLR 56 may communicate with HLR 28 for purposes ofmanaging the mobility of multi-mode mobile stations, such as multi-modemobile station 16. However, HLR 28 and WWAN 12 may identify multi-modemobile station 16 differently than WLAN 14. For example, HLR 28 and WWAN12 may identify multi-mode mobile station 16 by MIN, MDN, MSID, and/orESN, and may also require other information regarding multi-mode mobilestation 16. In some cases, VVLR 56 may have access to such WWANparameters of multi-mode mobile station 16 because the WWAN parametersmay have already been provisioned in PBX 36 and/or VVLR 56. In othercases, multi-mode mobile station 16 may transmit the WWAN parametersautomatically, e.g., in the service registration message of step 104. Instill other cases, VVLR 56 may request WWAN parameters from multi-modemobile station 16, such as MIN, MDN, MSCID, and/or ESN, as indicated bystep 108. Multi-mode mobile station 16 may then respond with therequested WWAN parameters, as indicated by step 110.

VVLR 56 may then send HLR 28 an IS-41 Registration Notification (REGNOT)message, as indicated by step 112. The REGNOT message indicates thatmulti-mode mobile station 16 is now operating in an area served by VVLR56, e.g., by identifying VVLR 56 as currently serving multi-mode mobilestation 16. The REGNOT message may identify multi-mode mobile station16, such as by MIN, MDN, MSID, and/or ESN, and may also identify VVLR56. For example, even though it is not an MSC, VVLR 56 may identifyitself by a “MSCID” for purposes of IS-41 signaling. The REGNOT messagemay also include other information.

In response to the REGNOT message of step 112, HLR 28 may update thedata record it maintains for multi-mode mobile station 16 to indicatethat multi-mode mobile station 16 is currently being served by VVLR 56.HLR 28 also sends VVLR 56 an IS-41 regnot response, as indicated by step114. The regnot response may include a service profile for multi-modemobile station 16, and VVLR 56 may store the service profile as part ofits data record for multi-mode mobile station 16. HLR 28 may also cancelany previous registrations. For example, if multi-mode mobile station 16had been previously been served by WWAN 12 and registered in VLR 26,then HLR 28 may send VLR 26 an IS-41 Registration Cancellation (REGCANC)message to cancel the registration of multi-mode mobile station 16 inVLR 26.

Although steps 112 and 114 have been described with respect to the IS-41protocols, it is to be understood that VVLR 56 may use other protocols,such as SIP, SIP-T, or H.323, for communicating with HLR 28. Forexample, VVLR 56 may use a SIP user agent, which may be located in PBX36, to communicate with media gateway controller 62, via packet switchednetwork 52, using the SIP protocol. Media gateway controller 62 may, inturn, communicate with HLR 28 using IS-41, converting between the SIPmessages used by VVLR 56 and the IS-41 messages used by HLR 28. Thisconversion may involve encapsulation/de-encapsulation of IS-41 messagesin SIP message and/or mapping between message types and messageparameters.

The service profile provided to VVLR 56 in step 114 may identify anycall origination services, call termination services, or other servicesthat multi-mode mobile station 16 subscribes to in WWAN 12. In someembodiments, PBX 36 may use this service profile information to providemulti-mode mobile station 16 with the same or similar services thatmulti-mode mobile station 16 would have when served by WWAN 12. In otherembodiments, PBX 36 may provide multi-mode mobile station 16 withservices that are different from the services that multi-mode mobilestation 16 would have when served by WWAN 12.

After multi-mode mobile station 16 associates with wireless access point48, multi-mode mobile station 16 may also become registered with callmanagement service 58. For example, if SIP is used to set up callsthrough packet-switched network 52, then a SIP user agent may send a SIPREGISTER message to call management service 58, as indicated by step116. FIG. 2 assumes that the SIP user agent is in PBX 36. Alternatively,however, multi-mode mobile station 16 may have its own SIP user agent,in which case the SIP REGISTER message may originate from multi-modemobile station 16. In response to the SIP REGISTER message, callmanagement service 58 may store an indication that multi-mode mobilestation 16 is reachable at WLAN 14. Call management service 58 may alsoassociate multi-mode mobile station 16 with a directory number that canbe used to reach multi-mode mobile station 16, e.g., a directory numberassigned to media gateway 60.

FIG. 3 is an exemplary call flow diagram illustrating an exemplaryprocess that may be used to route a call to multi-mode mobile station 16when multi-mode mobile station 16 is being served by WLAN 14. It is tobe understood that multi-mode mobile station 16 will at this pointalready be registered with VVLR 56, HLR 28, and call management service58, e.g., using signaling like that shown in FIG. 2 and described above.

The process may begin when a caller places a call to a directory numberassociated with multi-mode mobile station 16, for example, its MDN. Thecaller may place the call using a landline telephone, wirelesstelephone, or other communication device. In this case, the directorynumber is assigned to MSC 24, and MSC 24 receives the call. For example,PSTN 30 may route the call to MSC 24, or the call may originate from amobile station operating in an area served by MSC 24. Although thedirectory number of multi-mode mobile station 16 is assigned to MSC 24in this example, it is to be understood that the directory number couldbe assigned to other network elements instead, such as media gateway 60.

To locate multi-mode mobile station 16, MSC 24 may send HLR 28 an IS-41Location Request (LOCREQ) message, as indicated by step 200. The LOCREQmessage may identify multi-mode mobile station 16, e.g., by its MDN. Inresponse, HLR 28 refers to its data record for multi-mode mobile station16 and determines that multi-mode mobile station 16 was last known to beoperating in an area served by VVLR 56. Thus, HLR 28 sends VVLR 56 anIS-41 Route Request (ROUTEQ) message to obtain routing information thatcan be used to route the call to multi-mode mobile station 16, asindicated by step 202. The ROUTEREQ message may identify multi-modemobile station 16, such as by MIN, MDN, MSID, and/or ESN. In response,VVLR 56 sends HLR 28 an IS-41 routereq response that includes routinginformation that can be used to route the call to multi-mode mobilestation 16, as indicated by step 204.

The routing information can be in a variety of different forms. Forexample, the routing information could be a directory number. Thedirectory number may be assigned to a network element, such as PBX 36 ormedia gateway 60. The directory number may be used for multi-mode mobilestation 16 on only a temporary basis. For example, the directory numbermay be associated with multi-mode mobile station 16 for only during thetime when multi-mode mobile station 16 is being served by WLAN 14 oronly for purposes of this particular call to multi-mode mobile station16. Alternatively, the routing information could be an IP address, e.g.,an IP address of PBX 36, VVLR 56, or multi-mode mobile station 16. Othertypes of routing information could also be used, such as the host nameof PBX 36 or VVLR 56, or a SIP user name or address.

In the example shown in FIG. 3, the routing information in the routereqresponse of step 204 is a directory number (DN). HLR 28 forwards the DNto MSC 24 in an IS-41 locreq response message, as indicated by step 206.MSC 24 then routes the call to the DN, e.g., using an SS7 ISUP-IAMmessage. For example, if the DN is assigned to PBX 36, then MSC 24 mayuse an ISUP-IAM message to route the call to PBX 36, via PSTN 30. PBX 36may then alert multi-mode mobile station 16 of the incoming call.

However, in the example shown in FIG. 3, the DN is assigned to mediagateway 60. Thus, MSC 24 may use an ISUP-IAM message to route the callto media gateway 60 via PSTN 30, as indicated by step 208. The ISUP-IAMidentifies the DN as the called number. Media gateway controller 62receives the ISUP-IAM message and engages in signaling to set up a callleg through packet-switched network 52 to a network element associatedwith the DN. For example, media gateway controller 62 may send callmanagement service 58 a SIP INVITE message with the DN, as indicated bystep 210. In this case, PBX 36 has previously registered multi-modemobile station 16 with call management service 58 (step 116 shown inFIG. 2 and described above). Thus, call management service 58 may thensend PBX 36 a SIP INVITE message that identifies multi-mode mobilestation 16, as indicated by step 212. In response, PBX 36 may alertmulti-mode mobile station 16, as indicated by step 214. In this case,multi-mode mobile station 16 answers, as indicated by step 216.

As indicated by step 218, PBX 36 then sends call management service 58 a200 OK message to respond to the SIP INVITE message of step 212. The 200OK message may use SDP to describe various aspects of the session to beused for carrying the media exchanged in the call throughpacket-switched network 52. For example, the 200 OK message confirm thatRTP is to be used for the session and may specify that the RTP packetsare to be sent to a particular IP address. Call management service 58then sends media gateway controller 62 a 200 OK message, as indicated bystep 220. The 200 OK message of step 220 may include the sessiondescription from the 200 OK message of step 218.

When media gateway controller 62 receives the 200 OK message of step218, media gateway controller 62 may instruct media gateway 60 to createa connection between the call media gateway 60 received from MSC 24 (onthe circuit-switched side) and the RTP session described in the 200 OKmessage of step 220 (on the packet-switched side). For example, mediagateway controller 62 may send media gateway 60 an MGCP CreateConnectionmessage, as indicated by step 222. In response, media gateway 60 createsthe requested connection and sends media gateway controller 62 anacknowledgement, as indicated by step 224. Then, media gatewaycontroller 62 then sends call management service 58 an acknowledgement,as indicated by step 226, and call management service 58 sends PBX 36 anacknowledgement, as indicated by step 228.

At this point, the call is established between the caller and multi-modemobile station 16. The voice or other media exchanged between the callerand multi-mode mobile station 16 may be carried between MSC 24 and mediagateway, via circuit-switched network 32, in a PCM format, as indicatedby step 230, and may be carried between media gateway 60 and multi-modemobile station 16, via packet-switched network 52, in an RTP format, asindicated by step 232.

FIG. 4 shows an exemplary call flow for the case that VVLR 56 returns anIP address as the routing information to route a call to multi-modemobile station 16. The IP address may be associated with PBX 36 or withmulti-mode mobile station 16, for example. In addition, FIG. 4 assumesthat MSC 24 and media gateway 60 are connected by an intermachine trunk(IMT), e.g., IMT 64. The process may begin when MSC 24 receives a callto a directory number associated with multi-mode mobile station 16.Thus, MSC 24 may send HLR 28 a LOCREQ message, as indicated by step 300,and HLR 28 may send a ROUTEREQ message to VVLR 56, as indicated by step302, e.g., in a manner similar to the example of FIG. 3. In thisexample, however, VVLR 56 sends HLR 28 a locreq response that includesan IP address as the routing information to route the call to multi-modemobile station 16, as indicated by step 304.

Although steps 302 and 304 have been described with respect to the IS-41protocols, it is to be understood that VVLR 56 may use other protocols,such as SIP, SIP-T, or H.323, for communicating with HLR 28. Forexample, the communications between VVLR 56 and HLR 28 may occur viamedia gateway controller 62, which may convert between the IS-41protocol used by HLR 28 and the SIP or other protocol used by VVLR 56.

Once HLR 28 receives the routing information provided in step 304, HLR28 may communicate with media gateway controller 62 to set up a mediagateway, such as media gateway 60, that is able to route the call to theIP address obtained from VVLR 56. For example, HLR 28 may communicatewith media gateway controller 62, using IS-41 signaling, as if mediagateway controller 62 were an MSC. In particular, to set up the call HLR28 may send media gateway controller 62 a message that includes the IPaddress from VVLR 56, as indicated by step 306. HLR 28 may also sendmedia gateway controller 62 information regarding what vocoder formatsare supported by multi-mode mobile station 16.

In response, media gateway controller 62 acts to set up the call throughmedia gateway 60 to this IP address. Media gateway controller 62 mayalso identify an IMT trunk and port number that can be used for the callon the circuit-switched side of media gateway 60. Media gatewaycontroller 62 may send the trunk and port number to HLR 28, as indicatedby step 308. HLR 28 then sends the trunk and port number to MSC 24 in alocreq response message, as indicated by step 310. In response, MSC 24forwards the call to media gateway 60 using the specified trunk and portnumber, as indicated by step 312.

To set up the call through packet-switched network 52 from media gateway60, media gateway controller 62 may send call management service 58 aSIP INVITE message that invites a session with the IP address suppliedby VVLR 56, as indicated by step 314. Acting as a SIP proxy server, callmanagement service 58 forwards the SIP INVITE message to PBX 36, asindicated by step 316. In response, PBX 36 may alert multi-mode mobilestation 16, as indicated by step 318. Multi-mode mobile station 16 thenanswers, as indicated by step 320.

PBX 36 then sends a 200 OK message to call management service 58, asindicated by step 322, and call management service 58 sends a 200 OKmessage to media gateway controller 62, as indicated by step 324. Mediagateway controller 62 may then send media gateway 60 a MGCPCreateConnection message, as indicated by step 326. The CreateConnectionmessage instructs media gateway 60 to create a connection between thetrunk and port number used by MSC 24 and an RTP session with the IPaddress. Once media gateway 60 has created this connection, it respondswith an acknowledgement, as indicated by step 328. Media gatewaycontroller 62 then sends an acknowledgement to call management service58, as indicated by step 330, and call management service 58 sends anacknowledgement to PBX 36, as indicated by step 332.

At this point, the call is established between the caller and multi-modemobile station 16. The voice or other media exchanged between the callerand multi-mode mobile station 16 may be carried between MSC 24 and mediagateway 60, via the intermachine trunk, in a PCM format, as indicated bystep 334, and may be carried between media gateway 60 and mobile station16, via packet-switched network 52, in an RTP format, as indicated bystep 336.

Thus, the communication between VVLR 56 and HLR 28 help manage themobility of multi-mobile station 16 between WWAN 12 and WLAN 14. Asillustrated in FIGS. 3 and 4, when multi-mode mobile station 16 is beingserved by WLAN 14, multi-mode mobile station 16 can still be reached bydialing the same directory number (e.g., its MDN) that can be used toreach multi-mode mobile station 16 when it is being served by WWAN 12.

3. CONCLUSION

Exemplary embodiments of the present invention have been describedabove. Those skilled in the art will understand, however, that changesand modifications may be made to these embodiments without departingfrom the true scope and spirit of the invention, which is defined by theclaims.

1. A wireless local area network (WLAN) for providing wirelesstelecommunications services to a multi-mode mobile station, saidmulti-mode mobile station being able to wirelessly communicate with awireless wide area network (WWAN) when operating in a first wirelesscoverage area, said WWAN including a first data register that contains afirst data record for said multi-mode mobile station, wherein said firstdata register is a home location register (HLR), said WLAN comprising:at least one wireless access point providing a second wireless coveragearea, said multi-mode mobile station being able to wirelesslycommunicate with said at least one wireless access point when saidmulti-mode mobile station operates in said second wireless coveragearea; a private branch exchange (PBX) communicatively coupled to said atleast one wireless access point; and a second data register co-locatedwith said PBX and communicatively coupled to said first data register,wherein said second data register stores a second data record for saidmulti-mode mobile station when said multi-mode mobile station operatesin said second wireless coverage area, said second data register beingconfigured to transmit at least one mobility management message to saidfirst data register, whereby said at least one mobility managementmessage facilitates roaming between said first and second wirelesscoverage areas by said multi-mode mobile station.
 2. The WLAN of claim1, wherein said PBX is communicatively coupled to a packet-switchednetwork.
 3. The WLAN of claim 1, wherein said PBX is communicativelycoupled to a circuit-switched telephone network.
 4. The WLAN of claim 1,wherein said at least one mobility management message includes aregistration message that said second data register sends to said firstdata register when said multi-mode mobile station operates in saidwireless coverage area, said registration message identifying saidmulti-mode mobile station.
 5. The WLAN of claim 1, wherein said at leastone mobility management message includes a routing message, said routingmessage including routing information to route a call to said multi-modemobile station.
 6. The WLAN of claim 5, wherein said routing informationincludes a directory number associated with said PBX.
 7. The WLAN ofclaim 5, wherein said routing information includes a directory numberassociated with a media gateway communicatively coupled to said WLAN viaa packet-switched network.
 8. The WLAN of claim 5, wherein said routinginformation includes an Internet Protocol (IP) address of said PBX. 9.The WLAN of claim 5, wherein said routing information includes anInternet Protocol (IP) address of said multi-mode mobile station. 10.The WLAN of claim 1, wherein said second data register is a virtualvisitor location register.